1. Field of the Invention
The present invention relates generally to an electronic money safe for collectively managing electronic money representative of currency values in the form of electronic information, and more particularly to an electronic money safe for use in a transaction using IC cards.
2. Description of the Related Art
From the viewpoint of safety and convenience of settlement in the transaction such as buying and selling, a notice is recently being given to so-called electronic money utilizing electronic digital data as cashes as settling means in place of the conventional paper money, coins, etc. For this reason, banks and the like need be provided with electronic money safes for collectively managing the electronic money, and hence desire a provision of highly reliable safes.
In the settlement using the conventional electronic money, in order to secure the security, an IC card stores therein, for example, digital data representative of the electronic money, programs for transferring the electronic money, and a cryptographic processing circuit for use in the value transfer. Thus, upon the transaction, a direct data exchange of the electronic money is effected between the IC card of the user and the IC card of the part having business relations therewith. The exchange of electronic money between the two IC cards applies also to the case where a customer uses a load terminal to load electronic money from the bank side into the IC card. In this case also, a direct exchange of electronic money must be effected between the IC card of the customer and the IC card on the bank side. For this reason, the bank side possesses IC cards exceeding the number of customers expected to transact at one time, thereby enabling a direct exchange of electronic money between the IC cards of the customers and the IC card of the bank to be performed in response to the load demands of the customer. In order to meet the need for exchange of electronic money with the IC cards of the customers in this manner, use has hitherto been made of an electronic money safe storing a multiplicity of IC cards therein.
However, the electronic money safe storing a multiplicity of IC cards therein has entailed the following deficiencies. First is a problem of changing work of the cryptographic processing. In the electronic money transaction, cryptographic processing is performed upon the transfer of the electronic money although the strength of the cryptogram tends to lower year by year due to the progress of the technology and so forth. For this reason, typically, there is a need to change the cryptographic processing every several years. However, the electronic money safe using the IC cards stores therein several tens to several thousands of IC cards, so that a multiplicity of IC cards must be replaced every time the cryptographic processing is changed.
Then there arises a problem of reliability of the IC cards. The reliability (failure rate) of the IC cards being currently used is of the order of 100 fit (100 times/ 10.sup.9 H). Providing that 1000 IC cards are consecutively used for example, the failure frequency is given as EQU 109/ 100.times.1,000=10,000 H (about 1.2 years)
This means that the value may possibly become extinct about once a year.
Furthermore, there also arises a problem of service life of the IC cards. The rewritable number of times of the IC cards being currently used is of the order of 100,000, so that if one IC card is used for the transaction once a minute, its service life is given as EQU 100,000/ 60 (min/hour)=1,667 H (about 69 days)
This means that the IC cards must be replaced about once per two months.